linux-kernel - [PATCH AUTOSEL 4.19 485/671] cxgb4: smt: Add lock for atomic_dec_and

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Date:   Thu, 16 Jan 2020 12:02:03 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Chuhong Yuan <hslester96@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 485/671] cxgb4: smt: Add lock for atomic_dec_and_test

From: Chuhong Yuan <hslester96@...il.com>

[ Upstream commit 4a8937b83892cb69524291cae6cdabad4a8be033 ]

The atomic_dec_and_test() is not safe because it is
outside of locks.
Move the locks of t4_smte_free() to its caller,
cxgb4_smt_release() to protect the atomic decrement.

Fixes: 3bdb376e6944 ("cxgb4: introduce SMT ops to prepare for SMAC rewrite support")
Signed-off-by: Chuhong Yuan <hslester96@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/chelsio/cxgb4/smt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb4/smt.c b/drivers/net/ethernet/chelsio/cxgb4/smt.c
index 7b2207a2a130..9b3f4205cb4d 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/smt.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/smt.c
@@ -98,11 +98,9 @@ static struct smt_entry *find_or_alloc_smte(struct smt_data *s, u8 *smac)
 
 static void t4_smte_free(struct smt_entry *e)
 {
-	spin_lock_bh(&e->lock);
 	if (atomic_read(&e->refcnt) == 0) {  /* hasn't been recycled */
 		e->state = SMT_STATE_UNUSED;
 	}
-	spin_unlock_bh(&e->lock);
 }
 
 /**
@@ -112,8 +110,10 @@ static void t4_smte_free(struct smt_entry *e)
  */
 void cxgb4_smt_release(struct smt_entry *e)
 {
+	spin_lock_bh(&e->lock);
 	if (atomic_dec_and_test(&e->refcnt))
 		t4_smte_free(e);
+	spin_unlock_bh(&e->lock);
 }
 EXPORT_SYMBOL(cxgb4_smt_release);
 
-- 
2.20.1